In military and law enforcement terminology, a sniper rifle is a precision-rifle used to ensure more accurate placement of bullets at longer ranges than other small arms. A typical sniper rifle is built for optimal levels of accuracy, fitted with a telescopic sight and chambered for a military centerfire cartridge. The term is often used in the media to describe any type of accurized firearm fitted with a telescopic sight that is employed against human targets, although "sniping rifle" or "sniper's rifle" is the technically correct fashion to refer to such a rifle.The military role of a sniper (a term derived from the snipe, a bird which was difficult to hunt and shoot) dates back to the turn of the 18th century, but the true sniper rifle is a much more recent development. Advances in technology, specifically that of telescopic sights and more accurate manufacturing, allowed armies to equip specially trained soldiers with rifles that enable them to deliver precise shots over greater distances than regular infantry weapons. The rifle itself could be based on a standard rifle (at first, a bolt-action rifle); however, when fitted with a telescopic sight, it becomes a sniper rifle.

In the American Civil War Confederate troops equipped with barrel-length three power scopes mounted on the exceptionally accurate British Whitworth rifle had been known to kill Union officers at ranges of about 800 yards (731.5m), an unheard-of distance at that time.The earliest sniper rifles were little more than conventional military or target rifles with long-range "peep sights" and Galilean 'open telescope' front and rear sights, designed for use on the target range. Only from the beginning of World War I did specially adapted sniper rifles come to the fore. Germany deployed military caliber hunting rifles with telescopic sights, and the British used Aldis, Winchester and Periscopic Prism Co. sights fitted by gunsmiths to regulation SMLE Mk III and Mk III* or Enfield Pattern 1914 rifles; the Canadian Ross rifle was also employed by snipers after it had been withdrawn from general issue.Typical World War II-era sniper rifles were generally standard-issue battle rifles, selected for accuracy, with a 2.5x or 3x telescopic sight and cheek-rest fitted and the bolt turned down if necessary to allow operation with the scope fitted. Australia's No.1 Mk III* (HT) rifle was a later conversion of the SMLE fitted with the Lithgow heavy target barrel at the end of WW2. By the end of the war, forces on all sides had specially trained soldiers equipped with sniper rifles, and they have played an increasingly important role in military operations ever since.